Automatic vehicle exterior light control

ABSTRACT

A system and method of automatically controlling vehicle exterior lights including an image sensor and a controller to generate headlamp control signals.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/496,357, filed Jul.1, 2009, now U.S. Pat No. 8,462,204, which is acontinuation of U.S. patent application Ser. No. 11/122,880, filed May5, 2005, now U.S. Pat. No. 7,561,181, which is a continuation of U.S.patent application Ser. No. 10/324,679, filed on Dec. 20, 2002, now U.S.Pat. No. 6,891,563, which is a continuation of U.S. patent applicationSer. No. 08/952,026, filed under 35 U.S.C.§371, filed Nov. 19, 1997, nowU.S. Pat. No. 6,498,620.

BACKGROUND OF THE INVENTION

This invention relates generally to vision systems for vehicles and,more particularly, to rearview vision systems which provide the vehicleoperator with scenic information in the direction rearward of thevehicle. More particularly, the invention relates to a rearview visionsystem utilizing image capture devices, such as CMOS imaging arrays andthe like.

A long-felt need in the art of vehicle rearview vision systems is toreduce the amount of time spent gathering information of the conditionaround the vehicle in order to safely carry out a vehicle maneuver, suchas a turn or a lane change. It has been determined that up to about 50percent of maneuver time is spent gathering information withconventional rearview mirrors. This typically requires viewing one ormore mirrors, turning the head and body to check blind spots, anddouble-checking the mirrors prior to executing the maneuver. Someimprovement has been obtained by adjusting mirror optics, for example,to increase the observed field of view rearward of the vehicle. However,this is achieved with an increase in image distortion which makes driverawareness of conditions to the side and rear of the vehicle even moredifficult.

Another long-felt need in the art of vehicle rearview vision systems hasbeen to eliminate exterior rearview mirrors by utilizing image capturedevices, such as cameras, in combination

with dashboard displays. This would be beneficial because it wouldreduce wind drag on the vehicle, wind noise and vehicle weight.Furthermore, rearview mirrors protrude a substantial distance from theside of the vehicle, which makes maneuvering in tight spaces moredifficult. Image capture devices are capable of positioning in a greatervariety of locations on the vehicle, providing more flexibility ofvehicle styling. It is further expected that camera systems wouldgreatly reduce the blind spots to the sides and rear of the vehiclecommon with vehicles equipped with conventional rearview mirror systems.The driver cannot perceive vehicles, objects, or other road users insuch blind spots without turning his or her body, which interferes withforward-looking visual activities.

Camera-based rearview vision systems for vehicles have not obtainedcommercial acceptance. One difficulty with proposed systems has beenthat they present a large amount of visual information in a manner whichis difficult to comprehend. This difficulty arises from many factors. Inorder to significantly reduce blind spots, multiple image capturedevices are typically positioned at various locations on the vehicle.The image of an object behind the equipped vehicle is usually capturedby more than one image capture device at a time and displayed inmultiple images. This may confuse the driver as to whether more than oneobject is present. When multiple image capture devices are positioned atdifferent longitudinal locations on the vehicle, objects behind thevehicle are at different distances from the image capture devices. Thisresults in different image sizes for the same object. This effect isespecially noticeable for laterally extending images, such as a bridge,highway crosswalk markings, the earth's horizon, and the like. Suchimages are at different vertical angles with respect to the imagecapture devices. This results in different vertical positions on thedisplay causing the elongated image to appear disjointed.

A camera system provides a monocular view of the scene, compared to thebinocular stereoscopic view obtained when the scene is viewed through arearview mirror. This makes the ability to judge distances in a camerasystem a problem. This effect is most noticeable at distances close tothe vehicle where stereoscopic imaging is relied upon extensively by thedriver in judging relative locations of objects. Therefore, known camerasystems fail to provide to the driver important information where thatinformation is most needed at small separation distances fromsurrounding objects.

Another difficulty with camera systems is that, in order to provide asufficient amount of information, the camera system typically presentsthe driver with a greatly increased field of view. This improvesperformance by further reducing blind spots at the side and rear of thevehicle. However, an increased field of view is often obtained byutilizing a wide-angle lens which introduces distortion of the scene andfurther impairs the ability of the driver to judge distances of objectsdisplayed. The problem with such distortion of the scene is that thedriver must concentrate more on the display and take a longer time tointerpret and extract the necessary information. This further distractsthe driver from the primary visual task of maintaining awareness ofvehicles and other objects in the vicinity of the driven vehicle.

Yet an additional difficulty with camera systems is that flat paneldisplays present the image captured by the rearward-facing image capturedevice, or devices, at a focal length that approximates the arm lengthof the vehicle driver. In order to observe the condition of the vehicleutilizing the rearview vision system, the driver must change his or hergaze from the forward field of view of the vehicle to the display.Because the forward field of view of the vehicle is at a focal lengththat is much greater than the focal length of the displayed image, theeyes of the driver must refocus upon changing gaze. This refocusingfurther increases the amount of time for the driver to assimilate theinformation in the displayed image. Furthermore, when the gaze of thedriver returns to the forward field of view, the eyes must, again,refocus to the greatly longer distance.

Yet an additional difficulty with camera systems is that of findingadequate space in the crowded area of the vehicle's dashboard for thecomponents making up the display.

SUMMARY OF THE INVENTION

The present invention is directed towards enhancing the interpretationof visual information in a rearview vision system by presentinginformation in a manner which does not require significant concentrationof the driver or present distractions to the driver. This isaccomplished according to an aspect of the invention in a rearviewvision system having at least two image capture devices positioned onthe vehicle and directed generally rearwardly with respect to thedirection of travel of the vehicle. A display is provided for imagescaptured by the image capture devices. The display displays an imagesynthesized from outputs of the image capture devices which approximatesa rearward-facing view from a single location. In order to obtain all ofthe necessary information of activity, not only behind but also alongside of the vehicle, the virtual camera should be positioned forward ofthe driver. The image synthesized from the multiple image capturedevices may have a dead space which corresponds with the area occupiedby the vehicle. This dead space is useable by the driver's sense ofperspective in judging the location of vehicles behind and along side ofthe equipped vehicle.

The present invention provides techniques for synthesizing imagescaptured by individual, spatially separated, image capture devices intosuch ideal image, displayed on the display device. This may beaccomplished, according to an aspect of the invention, by providing atleast three image capture devices. At least two of the image capturedevices are side image capture devices mounted on opposite sides of thevehicle. At least one of the image capture devices is a center imagecapture device mounted laterally between the side image capture devices.A display system displays an image synthesized from outputs of the imagecapture devices. The displayed image includes an image portion from eachof the image capture devices. The image portion from the center imagecapture device is vertically compressed.

It has been discovered that such vertical compression substantiallyeliminates distortion resulting from the spatial separation between thecameras and can be readily accomplished. In an illustrated embodiment,the image compression is carried out by removing selective ones of thescan lines making up the image portion. A greater number of lines areremoved further away from the vertical center of the image.

The compression of the central image portion produces a dead space inthe displayed image which may be made to correspond with the area thatwould be occupied by the vehicle in the view from the single virtualcamera. Preferably, perspective lines are included at lateral edges ofthe dead space which are aligned with the direction of travel of thevehicle and, therefore, appear in parallel with lane markings. Thisprovides visual clues to the driver's sense of perspective in order toassist in judging distances of objects around the vehicle.

According to another aspect of the invention, image enhancement meansare provided for enhancing the displayed image. Such means may be in theform of graphic overlays superimposed on the displayed image. Suchgraphic overlap may include indicia of the anticipated path of travel ofthe vehicle which is useful in assisting the driver in guiding thevehicle in reverse directions. Such graphic overlay may include adistance grid indicating distances behind the vehicle of objectsjuxtaposed with the grid.

According to yet an additional aspect of the invention, a rearviewvision system for a vehicle includes at least one image capture devicepositioned on the vehicle and directed generally rearwardly with respectto the direction of travel of the vehicle. A display system is providedwhich displays a rear image synthesized from an output of the imagecapture device. The rear image is substantially contiguous with theforward field of view of the vehicle driver and at a focal length thatis forward of the vehicle passenger compartment and preferably withinthe depth of field of a vehicle driver viewing a distant object. Becausethe image has a focal length that more closely matches that of theforward field of view observed by the driver, the need for the driver'seyes to refocus from the forward field of view to a much shorter focusdistance each time the gaze of the driver is directed at the displaysystem is minimized. This reduces the amount of time required for thedriver to gaze at the displayed image and interpret objects displayed inthe image. Furthermore, the reduction in the repeated refocusing of thedriver's eyes reduces driver fatigue. If there are any near fieldobjects in the periphery of the driver's forward field of view, such aswindshield wipers, windshield frame, dashboard, and the like, thedisplay system is preferably positioned in a manner which blocks theview of such near field objects. In this manner, the driver's gaze mayshift between the forward field of view and the long focal lengthdisplay system without being refocused on the near field objects. Thisis based upon a recognition that the driver's eyes will tend to refocuson the near field object momentarily even though the gaze is beingredirected between the forward field of view and the display system.

According to yet an additional aspect of the invention, a rearviewvision system for a vehicle includes at least one image capture devicepositioned on the vehicle and directed generally rearwardly with respectto the direction of travel of the vehicle. A display system is providedfor displaying a rear image captured by the image capture device. Thedisplayed image is a unitary image having an aspect ratio that isbetween approximately 4:1 and approximately 2:1. In a most preferredembodiment, the image has an aspect ratio that is approximately 8:3. Theaspect ratio, according to this aspect of the invention, is especiallyuseful where the unitary image is synthesized from a plurality of imageswhich are captured by a plurality of image captured devices and aretiled by the display device.

According to yet an additional aspect of the invention, a rearviewvision system for a vehicle includes a plurality of image capturedevices positioned on the vehicle and directed generally rearwardly withrespect to the direction of travel of the vehicle. A display systemwhich includes at least one image generator and an optical correctionsystem is provided which displays an image synthesized from outputs ofthe image capture devices as a unitary image. Alternatively, the displaysystem may include a plurality of image generators, each associated withone or more of the image capture devices and an optical correctionsystem which amplifies images generated by the image generators andmerges them into a unitary image. The optical correction systemadditionally increases the focal length, or lengths, of the image, orimages, generated by the image generator, or generators. The displaysystem may be an opaque projection display which is positionedapproximately at the driver's arm length in front of the driver.Alternatively, the display system may be a view-through heads-up displaywhich projects the unitary image onto a combiner in order to combine theunitary image with the forward field of view of the driver.

These and other objects, advantages, and features of this invention willbecome apparent by review of the following specification in conjunctionwith the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a vehicle having a rearview vision systemaccording to the invention;

FIG. 2 is a side elevation of the vehicle in FIG. 1;

FIG. 3 is a front elevation of a display according to the invention;

FIG. 4 is the same view as FIG. 1 illustrating an alternative embodimentof the invention;

FIG. 5 is a block diagram of an electronic system according to theinvention;

FIG. 6 is the same view as FIG. 3 illustrating an alternate mode ofoperation of the system;

FIG. 7 is the same view as FIG. 2 illustrating an alternative embodimentof the invention;

FIG. 8 is the same view as FIG. 3 illustrating an alternative embodimentof the invention;

FIG. 9 is the same view as FIGS. 1 and 4 illustrating an alternativeembodiment of the invention;

FIG. 10 is the same view as FIGS. 3 and 8 illustrating an alternativeembodiment of the invention;

FIG. 11 is a chart illustrating the horizontal row of pixels (n1, n2) onwhich an object will be imaged from two longitudinally separated imagecapture devices as that object is spaced at different longitudinaldistances from the image capture devices;

FIG. 12 is a forward elevation of a vehicle passenger compartment asviewed by a vehicle driver;

FIG. 13 is a sectional view taken along the lines XIII-XIII in FIG. 12;

FIG. 14 is a sectional view taken along the lines XIV-XIV in FIG. 12;

FIG. 15 is the same view as FIG. 14 of an alternative embodiment;

FIG. 16 is the same view as FIG. 14 of another alternative embodiment;

FIG. 17 is an enlarged view of the display system in FIG. 14illustrating details thereof;

FIG. 18 is a block diagram similar to FIG. 5 of an alternativeembodiment of the invention;

FIG. 19 is a side elevation similar to FIG. 2 of an alternativeembodiment of the invention;

FIG. 20 is an enlarged side elevation of an image capture device withportions of the housing removed in order to reveal internal structurethereof;

FIG. 21 is a block diagram similar to FIG. 5 of another alternativeembodiment of the invention;

FIG. 22 is a block diagram similar to FIG. 5 of another alternativeembodiment of the invention;

FIG. 23 is a block diagram similar to FIG. 5 of another alternativeembodiment of the invention;

FIG. 24 is a block diagram similar to FIG. 5 of another alternativeembodiment of the invention; and

FIG. 25 is a block diagram of a rearview vision system having extendeddynamic range capabilities.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now specifically to the drawings, and the illustrativeembodiments depicted therein, a vehicle 10, which may be an automobile,a light truck, a sport utility vehicle, a van, a bus, a large truck, orthe like includes a rearview vision system, generally illustrated at 12,for providing a driver of the vehicle with a view rearwardly of thevehicle with respect to the direction of travel T of the vehicle (FIG.1). Vision system 12 includes at least two side image capture devices 14positioned, respectively, on opposite sides of vehicle 10 and a centerimage capture device 16 positioned on the lateral centerline of thevehicle. All of the image capture devices are directed generallyrearwardly of the vehicle. Rearview vision system 12 additionallyincludes an image processor 18 for receiving data signals from imagecapture devices 14, 16 and synthesizing, from the data signals, acomposite image 42 which is displayed on a display 20.

As will be set forth in more detail below, the images captured by imagecapture devices 14, 16 are juxtaposed on display 20 by image processor18 in a manner which approximates the view from a single virtual imagecapture device positioned forwardly of the vehicle at a location C andfacing rearwardly of the vehicle, with the vehicle being transparent tothe view of the virtual image capture device. Vision system 12 providesa substantially seamless panoramic view rearwardly of the vehiclewithout duplicate or redundant images of objects. Furthermore,elongated, laterally-extending, objects, such as the earth's horizon,appear uniform and straight across the entire displayed image. Thedisplayed image provides a sense of perspective, which enhances theability of the driver to judge location and speed of adjacent trailingvehicles.

Each of side image capture devices 14 has a field of view 22 and isaimed rearwardly with respect to the vehicle about an axis 24 which isat an angle, with respect to the vehicle, that is half of the horizontalfield of view of the image capture device. In this manner, each of theimage capture devices 14 covers an area bounded by the side of thevehicle and extending outwardly at an angle defined by the horizontalfield of view of the respective side image capture device. Center imagecapture device 16 has a horizontal field of view 26, which issymmetrical about the longitudinal axis of the vehicle. The field ofview of each side image capture device 14 intersect the field of view ofcenter image capture device 16 at a point P which is located a distanceQ behind vehicle 10.

Rear blind zones 30 are located symmetrically behind vehicle 10extending from the rear of the vehicle to point P. Side blind zones 25located laterally on respective sides of the vehicle extend rearwardlyof the forward field of view 36 of the driver to the field of view 22 ofthe respective side image capture device 14. An object will not becaptured by side image capture devices 14 or center image capture device16 if the object is entirely within one of the blind zones 25, 30. Inorder for an object, such as another vehicle V or other road usertravelling to the side of vehicle 10, to be observed by an operator ofvehicle 10, the object must be either at least partially within theforward field of view 36 of the driver or be captured by image capturedevices 14, 16 and displayed on display 20. FIG. 4 illustrates vehicle10 travelling on a three-lane highway having lanes L1, L2, and L3 withthe vehicle in lane L2. Another vehicle V is shown positioned mostlywithin one of the blind zones 25, but with the rearmost portion of thevehicle V extending into field of view 22 where the vehicle image willbe captured by one of side image capture devices 14. In the illustratedembodiment, vehicle V is a motorcycle travelling in the center of lanesL1 or L3 and represents a worst case for observing a vehicle travellingat least partially within one of the blind zones 25. In order for aportion of vehicle V to be extending either forwardly or rearwardly ofthe respective blind zone 25, where the vehicle V may be observed byeither the forward field of view 36 of the driver or by the rearviewvision system 12, the field of view 22 of side image capture devices 14must be sufficiently wide to capture a portion of vehicle V asillustrated in FIG. 4. Preferably, the horizontal field of view 22 ofside image capture devices 14 is no greater than that required toprovide sufficient coverage which would be in the range of betweenapproximately 55 degrees and approximately 70 degrees. In theillustrated embodiment, the horizontal field of view 22 is 61 degrees.In order for a portion of vehicle V to be within a vertical field ofview 40 of one of side image capture devices 14, the field of viewshould extend to the pavement at a plane M which intersects vehicle V(FIG. 2). Preferably, vertical field of view 40 is between approximately60 degrees and approximately 75 degrees. In the illustrated embodiment,vertical field of view 40 is 66 degrees.

A left overlap zone 32 and a right overlap zone 34 extend rearward fromrespective points P where the horizontal fields of view of the sideimage capture devices intersect the field of view of center imagecapture device 16. Overlap zones 32, 34 define areas within which anobject will be captured both by center image capture device 16 and oneof the side image capture devices 14. An object in an overlap zone 32,34 will appear on display 20 in multiple image portions in a redundantor duplicative fashion. In order to avoid the presentation of redundantinformation to the driver, and thereby avoid confusion and simplify thetask of extracting information from the multiple images or combinedimages on display 20, the object should avoid overlapping zones 32, 34.In practice, this may be accomplished to a satisfactory extent by movingpoints P away from the vehicle and thereby increasing distance Q. It isdesirable to increase distance Q to a length that will exclude vehiclestravelling at a typical separation distance behind vehicle 10 fromoverlapping zones 32, 34. This separation distance is usually a functionof the speed at which the vehicles on the highway are travelling.Therefore, optionally, distance Q may be made variable, not fixed. Insuch embodiment, the faster the vehicles are travelling, the further Qshould be moved behind vehicle 10 to keep overlap zones 32 and 34outside of the recommended vehicle spacing. If, however, the vehiclesare travelling at a slower speed, then the generally acceptedrecommendation for vehicle spacing decreases and it is more likely thata vehicle will be within overlap zone 32, 34. Therefore, the distance Qmay be selected to accommodate expected vehicle spacing for an averagedriving speed of vehicle 10.

Distance Q is a function of the effective horizontal field of view 26 ofcenter image capture device 16. As field of view 26 decreases, points Pmove further rearward of the vehicle from a distance Q1, to a distanceQ2, as best illustrated in FIG. 4. In order to increase distance Q toeliminate redundant and duplicative information displayed on display 20for most driving conditions of vehicle 10, field of view 26 ispreferably less than 12 degrees. In the illustrated embodiment, field ofview 26 is between 6 and 8 degrees. Alternatively, distance Q may bedynamically adjusted according to some parameter, such as the speed ofvehicle 10. This would allow Q to be greater when the vehicle istravelling at a faster speed, where vehicle separation tends to belarger, and vice versa. Field of view 26 may be adjusted by utilizing aselective presentation of pixels of the captured image in the displayedimage.

Referring to FIG. 3, image display device 20 displays a composite image42 made up of a left image portion 44, a right image portion 46, and acenter image portion 48. Each image portion 44-48 is reversed from theimage as captured by the respective image capture device 14, 16utilizing conventional techniques. These techniques include reading theimage in reverse with the image capture device, writing the image inreverse to display device 20, or reversing the image in image processor18. Left image portion 44 is joined with central image portion 48 at aboundary 50. Central image portion 48 is joined with right image portion46 at a boundary 52. As may best be seen in FIG. 3, the image portionsat boundaries 50 and 52 are continuous whereby composite image 42 is aseamless panoramic view rearwardly of the vehicle. As also is apparentfrom FIG. 3, central image portion 48 is narrower than either left imageportion 44 or right image portion 46. This is a result of reducing thehorizontal field of view 26 of center image capture device 16sufficiently to move points P, and thus overlap zones 32 and 34, asufficient distance behind vehicle 10 to reduce redundant andduplicative images between image portions 44-48. Composite image 42provides a clear image, which avoids confusion and simplifies the taskof extracting information from the multiple image portions 44-48. Asalso may be seen by reference to FIG. 3, display 20 may additionallyinclude indicia such as the readout of a compass 54, vehicle speed 56,turn signals 58, and the like as well as other graphical or videodisplays, such as a navigation display, a map display, and aforward-facing vision system. In this manner, rearview vision system 12may be a compass vision system or an information vision system.

In the embodiment of rearview vision system 12 having a dynamicallyadjusted value of distance Q, the spacing between boundaries 50 and 52will dynamically adjust in sequence with the adjustment of distance Q.Thus, as overlap zones 32, 34 move further away from the vehicle; forexample, in response to an increase in speed of the vehicle, boundarylines 50 and 52 will move closer together and vice versa. In thismanner, composite image 42 is dynamic, having image portions ofdynamically adaptive sizes.

Display 20 is of a size to be as natural as possible to the driver. Thisis a function of the size of the displayed image and the distancebetween the display and the driver. Preferably, the displayed imagesimulates an image reflected by a rearview mirror. As such, the size ofthe displayed image is approximately the combined areas of the threerearview mirrors (one interior mirror and two exterior mirrors)conventionally used with vehicles. As best seen by reference to FIGS. 2and 12, display 20 is preferably positioned within the driver'sphysiological field of view forward of the vehicle, generallyillustrated at 70, through the windshield 72 without significantlyobstructing the forward field of view. It is known that the driver'sfield of view, with the head and eyes fixed forward, extends further ina downward direction than in an upward direction. Display 20 could belocated above the field of view 70 wherein the display may be observedat the upward portion of the driver's field of view. However, theposition for the display illustrated in FIGS. 2 and 12 is preferredwherein the display is within the lower portion of the driver's field ofview.

Display 20 may be a direct view flat panel display, such as a back-litor reflective liquid crystal display, a plasma display, a field emissiondisplay, a cathode ray tube electroluminescent, light-emitting diode ordeformable mirror display. The display may be mounted/attached to thedashboard, facia or header, or to the windshield at a positionconventionally occupied by an interior rearview mirror. However, thesynthesized image could be displayed using other display techniques suchas to provide a projected or virtual image. Alternatively, a virtualimage may be displayed on an opaque display adjacent the forward fieldof view. Alternatively, a virtual image may be displayed on aview-through heads-up display in which the image is superimposed on theforward field of view.

In the embodiment illustrated in FIGS. 12-17, display 20 displays animage at a focal length that is forward of the passenger compartment ofvehicle 10. Preferably, the image displayed by display 20 is at a focallength that is within the driver's normal depth of field when viewing adistant object. Display 20 includes an image generator 74, whichproduces an image captured by one or more image capture devices 14, 16,and an optical correction system 76, which increases the focal distanceof the image generated by image generator 74. In the illustratedembodiment, optic correction system 76 increases the focal distance bycollimating the rays, generally indicated at X, from diverging rays togenerally parallel rays projected from the display. Optical correctionsystem 76 additionally magnifies the image. In the illustratedembodiment, the magnification is a factor of two. In this manner,optical corrective system 76 has the advantage of extending the focaldistance of the image generated by image generator 74 and enlarging theimage by the factor of magnification thereof. This advantageously allowseach image generator 74 to project all or a portion of an image capturedby one of image capture devices 14, 16, or a combination of portions ofimages from one or more image capture devices, by tiling the images orimage portions. This is accomplished because the images projected fromoptical correction system 76 may abut even though the correspondingimage generators 74 do not. This provides a convenient technique forjoining the images synthesized from the image capture devices into aunitary image which represents a panoramic view rearward of the vehicle.

In the embodiment illustrated in FIG. 14, display 20 is an opaqueprojection display which projects the image directly toward the driver.In the embodiment illustrated in FIG. 15, a display device 120 is aview-through heads-up display in which the rays X are projectedgenerally upwardly by image generator 74 and optical correction system76 which are generally vertically aligned, or aligned forward ofvertical. The rays X are reflected off a first surface of windshield 72in the direction of the driver. Windshield 72 acts as a combiner whichcombines the image displayed by display 120 with a portion of theforward field of view 70 observed by the driver. In the embodimentillustrated in FIG. 15, a combiner other than the windshield may beused. Examples may be holographic or diffractive optical film elementsor beam splitters of metal or dielectric thin films. Furthermore, imageprocessor 18 may generate a line in the shape of a polygon, such as arectangle, around rear image 42. This provides a border around the imageto differentiate the rear view from the view forward of the vehicle.

In the embodiment illustrated in FIG. 16, display 20A is oriented at anangle with respect to the forward field of view of driver D. Image raysX are reflected by a mirror 140 toward the driver. Display 20A is anopaque display, with mirror 140 blocking the driver's view of near fieldobjects, such as wipers 98 and the like. Display 20A has the advantageof being capable of location within a forward portion of the dashboard.Additionally, the only portion of the display visible to the driver ismirror 140. This allows near field portions of the display to besignificantly reduced.

Because display 20 has a relatively long focus distance, display 20defines an observation cone, generally designated 78, within which thedisplayed image can be observed. Therefore, the head of the driver mustbe properly oriented with respect to observation cone 78 in order toallow the driver to observe the displayed image. However, drivers comein various sizes. Therefore, a driver may be too tall or too short tohave his or her head properly positioned within observation cone 78. Inorder to provide for various size drivers along with various adjustmentsin seating positions and the like, an accommodation means, generallyillustrated at 80, may be provided in order to accommodate variations inthe relationship between a driver's head and observation cone 78. In theillustrated embodiment, accommodation means 80 includes adjustment means82 for adjusting the position of observation cone 78. The adjustmentmeans may adjust the position of the observation cone either vertically,horizontally, or both vertically and horizontally. A vertical adjustmentmeans 82 is illustrated in FIG. 13 in which the adjustment meansincludes an electric actuator 84 which is joined by linkage 86 with aportion of a housing 88 of display 20. Actuator 84 is electricallyinterconnected through a reversing switch 90 with a driver-operatedactuator 92 which may be positioned on dashboard 94 or other convenientposition accessible to the driver. Housing 88 may be adjustably mounted,such as by a pivot 96, in order to allow housing 88 to be adjustablyrepositioned with respect to dashboard 94. In this manner, by operationof actuator 92, housing 88 may be pivoted upwardly or downwardly withrespect to pivot 96 in order to adjust the direction of observation cone78. In this manner, the location of observation cone 78 may be adjustedin order to coincide with the location of the driver's head. In asimilar fashion, the position of observation cone 78 may be adjustedlaterally, if desired. If a view-through heads-up display of the typeillustrated in FIG. 15 is utilized, the position of the observation conemay be adjusted vertically and laterally, in a similar manner, bymechanical or optical adjustments of display 20.

Accommodation means 80 may include extending the rearward field of viewdisplayed by display 20 laterally outwardly with respect to the bezel 89beyond that normally observed by a driver, In this manner, a driver'shead located generally centrally within observation cone 78 will observea view generally rearwardly of the vehicle. As the driver's head ismoved laterally within observation cone 78, the driver will observeimages more laterally to the side of the vehicle as would occur if thedriver's head were to be moved with respect to a conventional opticalrearview mirror system.

Vehicle 10 may include one or more near field view objects adjacentforward field of view 70. One such object is a windshield wiper 98 ofthe vehicle. Other such objects may include the top of dashboard 94, theframe around windshield 72, the hoodline, and the like. The housing ofdisplay 20 in FIG. 14 and mirror 140 in FIG. 15 are positioned withrespect to forward field of view 70 such that housing 88 or mirror 140covers any near field of view objects in the portion of the forwardfield of view adjacent display 20, 20A. In this manner, the gaze of thedriver can switch between forward field of view 70 and the imagedisplayed on display 20, without the eyes of the driver focusing on anysignificant near field objects. This is based upon a discovery that,even though the eyes of the driver are switching between the long focaldistance of the forward field of view and the long focal distance of theimage displayed by display 20, the eyes of the operator willunconsciously momentarily focus on any near field object positionedbetween the long focal distance views. Therefore, by blocking thedriver's gaze of any near field objects, the eyes of the driver will beless stimulated to refocus during the transition from field of view 70to display 20 and back again.

Image processor 18, which supplies a video signal 100 to image generator74, may have a second input 102 which modulates the intensity level ofthe image generated by image generator 74 and displayed by display 20(FIG. 14). The illumination level of the display is set in response toan ambient light input 104 which is an indication of the ambient lightlevel around vehicle 10. Image processor 18 responds to the value ofambient light input 104 by producing a luminance intensity signal 102which increases the intensity of the display in response to increases inambient light level and decreases the intensity of the display inresponse to decreases in ambient light level. However, the level ofdisplay luminance may be limited to vary between upper and lower limitssuch that, once ambient light reaches a particular upper level, furtherincreases in ambient light level will not result in a further increasein display intensity. Likewise, once the ambient light level decreasesbelow a particular value, further reductions in ambient light level willnot result in further reduction in display intensity. Ambient lightinput 104 may be produced by a separate ambient light sensor of the typewhich produces a continuously variable output in response to variationsin ambient light levels, in which case, the intensity of display 20 maybe proportionately adjusted. Alternatively, ambient light input 104 maybe produced by a vehicle headlight control system (not shown) whichswitches the vehicle headlights on, or to a nighttime condition, inresponse to decreases in ambient light levels and switches the vehicleheadlights off, or to a daytime running light condition, in response toincreasing ambient light levels. Such system is disclosed in commonlyassigned U.S. patent application Ser. No. 08/277,674 filed on Jul. 19,1994, by Kenneth L. Schierbeek and Niall R. Lynam for an AUTOMATICREARVIEW MIRROR SYSTEM WITH AUTOMATIC HEADLIGHT ACTIVATION, thedisclosure of which is hereby incorporated herein by reference. If theambient light signal supplied to ambient light input 104 is a binarysignal representative of a daytime ambient light level and a nighttimeambient light level, image processor 18 would typically provide a signalon luminance intensity line 102 that would switch the intensity level ofdisplay 20 between two intensity levels. Alternatively, ambient lightinput 104 may be supplied with a signal developed by one or more imagecapture devices 14, 16. The ambient light signal would be based upon anaverage intensity value sensed by all, or a group of, pixels in theimage capture device or devices. This embodiment eliminates thenecessity for a separate ambient light sensor. Alternatively, ambientlight input 104 may be responsive to manual actuation of the vehicle'sheadlights by the driver. Additionally, a comfort level setting may beprovided to allow the driver to adjust to a preferred brightness at oneambient light condition. Thereafter, the system automatically adjustsdisplay brightness according to ambient light changes.

In the illustrated embodiment, display 20 incorporates a combined imagegenerator and optical correction system 106 which provides for bothimage magnification and light ray collimation. In this manner, the imageprojected from display 20 is larger than the image generated by imagegenerator 74 and has a focal length that is greater than the separationdistance between the image generator and the driver and, preferably, isgenerally at infinity (FIG. 17). Combined image generator and an opticalcorrection system 106 is disclosed in detail in U.S. Pat. No. 5,050,966for an OPTICAL COMBINER COLLIMATING APPARATUS; U.S. Pat. No. 4,859,031for an OPTICAL COLLIMATING APPARATUS; U.S. Pat. No. 4,900,133 for aHEADS-UP DISPLAY COMBINER UTILIZING A CHOLESTERIC LIQUID CRYSTALELEMENT; U.S. Pat. No. 4,987,410 for a MULTIPLE IMAGE FORMING APPARATUS;and U.S. Pat. No. 5,408,346 for an OPTICAL COLLIMATING DEVICE EMPLOYINGCHOLESTERIC LIQUID CRYSTAL AND NON-TRANSMISSIVE REFLECTOR, thedisclosures of which are hereby incorporated herein by reference andwill not be repeated. Suffice it to say, combined image generator andoptical correction system 106 includes a light source 108 whichgenerates broad band white light which is gathered and reflected by aparabolic reflector 110. In the illustrative embodiment, light source108 is a tungsten halogen incandescent lamp. The light rays then passthrough a dielectric green filter 112 which passes light in a specificregion of the green portion of the spectrum and through a hot mirror 114which removes the infrared content of the spectrum. Light then passesthrough a holographic diffuser 116 which homogenizes and shapes thelight pattern. The light rays then pass through a monochrome liquidcrystal display with opposing linear polarizers 118 which is suppliedwith a video signal by image processor 18. Items 108-118 make up imagegenerator 74, which, in the illustrative embodiment, is a transmissivebacklit liquid crystal display. However, image generator 74 couldadditionally be an emissive display or a reflective display, all ofwhich are well known in the art.

Light rays of the image generated by image generator 74 next passthrough an anti-reflective coated cover glass 120 which is joined with aleft-hand circular polarizer 122 which is bonded to this cover glass.The opposite surface of circular polarizer 122 is bonded to a lens 124having a 50/50 dielectric coating. Such dielectric coating allows lightrays to be both transmitted through the lens and reflected by the lens.The left-hand polarized light X′ transmitted through lens 124 contacts acholesteric liquid crystal layer (CLC) 126 which is left-hand polarized,which is what gives efficient reflection of left-hand polarized lightX′, as illustrated at X″. Fifty percent (50%) of light rays X″ getefficiently reflected by the 50/50 beam splitter on lens 124 asright-hand circular polarized light X′″. Right-hand polarized light X′″is transmitted by CLC layer 126 and passes through a right-hand circularpolarizer 128 and an anti-reflective coated cover glass 130.

As can be seen by reference to FIG. 17, the optical configuration oflens 124 in combination with the left-hand and right-hand circularpolarizers 122, 128 and cholesteric liquid crystal layer (CLC) 126,provide image magnification as well as collimate the image light inorder to produce a very long focal distance image. Advantageously, thisstructure allows image portions from multiple image capture devices tobe tiled into a unitary image. FIG. 17 illustrates an approach using asingle image generator. Merging of multiple image portions would requireadditional combined image generator and optical correction systems.Although image generators 74 for each of the image portions arelaterally spaced apart from each other, the amplification produced bycombined image generator and optical correction system 106 causes theimage portions to merge at their periphery. FIG. 17 illustrates anapproach using a single image generator. Merging of multiple imageportions would require additional combined image generators and opticalcorrection systems. Other optical elements such as prisms, or otherlenses, may be necessary to merge images to form a unitary image.Although the invention is illustrated with a combined image generatorand optical correction system using cholesteric liquid crystal opticalprocessing, other optical correction systems, as are known in the art,may be used. What is required is that the optical system generallycollimates the light generated by the image generator and, preferably,provides amplification to the generated image.

In the illustrated embodiment, rear image 42, synthesized from theoutput of image capture devices 14, 16, has a lateral width versesvertical height aspect ratio that is between approximately 4:1 and 2:1.Most preferably, the aspect ratio of image 42 is 8:3. This allows apanoramic view rearwardly of the vehicle with an optimum informationcontent while reducing display of irrelevant information. The aspectratio of display 20 may be different from that of the displayedsynthesized image 42. The remaining portion of the display, either aboveor below image 42, may be utilized to display images other thansynthesized image 42. For example, the remaining portion of the displaycan be used to display auxiliary information such as one or morevehicle-operating parameters, such as vehicle speed indicia 56, headingindicia 54, or turn signal indicia 58. Alternatively, the remainingportion of the display can be a reconfigurable high-information contentdisplay area to selectively display various types of information. Suchinformation may include incoming facsimile or pager information, phonenumbers, and navigational aids including pull-up maps, route guidanceinformation, global positioning system (GPS) data, intelligent vehiclehighway system (IVHS) information, as well as radio and environmentalsystem control settings, and the like. Display 20 is especially usefulfor displaying such alternative data. Because display 20 has a very longfocal length, the driver may consult the alternative data by switchingthe gaze of the driver between forward field of view 70 and to display20 which does not require extensive refocusing of the driver's eyes.This allows the driver to consult the alternative data quickly withreduced fatigue and distraction. The content of the auxiliaryinformation displayed may be user-selectable by a keypad, trackball, orother input device on the dashboard, steering column, or other positionreadily accessible to the driver.

Although various camera devices may be utilized for image capturedevices 14, 16, an electro-optic, pixilated imaging array, located inthe focal plane of an optical system, is preferred. Such imaging arrayallows the number of pixels to be selected to meet the requirements ofrearview vision system 12. The pixel requirements are related to theimaging aspect ratio of the respective image capture devices, which, inturn, are a function of the ratio of the vertical-to-horizontal field ofview of the devices, as is well known in the art. In the illustratedembodiment, the imaging aspect ratio of side image capture devices 14 is2:1 and the image aspect ratio of central image capture device 16 isvariable down to 0.1:1. Such aspect ratio will produce images which willnot typically match that of commercially available displays. Acommercially available display may be used, however, by leaving ahorizontal band of the display for displaying alpha-numeric data, suchas portions of an instrument cluster, compass display, or the like, asillustrated in FIG. 3.

In the illustrated embodiment, image capture devices 14, 16 are CMOSimaging arrays of the type manufactured by VLSI Vision Ltd. ofEdinburgh, Scotland, which are described in more detail in co-pendingU.S. patent application Ser. No. 08/023,918 filed Feb. 26, 1993, byKenneth Schofield and Mark Larson for an AUTOMATIC REARVIEW MIRRORSYSTEM USING A PHOTOSENSOR ARRAY, now U.S. Pat. No. 5,550,677, thedisclosure of which is hereby incorporated herein by reference. However,other pixilated focal plane image-array devices, which are sensitive tovisible or invisible electromagnetic radiation, could be used. Thedevices could be sensitive to either color or monochromatic visibleradiation or near or far infrared radiation of the type used innight-vision systems. Each image capture device could be a combinationof different types of devices, such as one sensitive to visibleradiation combined with one sensitive to infrared radiation. Examples ofother devices known in the art include charge couple devices and thelike.

Preferably, image capture devices 14 and 16 are all mounted at the samevertical height on vehicle 10, although compromise may be required inorder to accommodate styling features of the vehicle. The horizontal aimof image capture devices 14 and 16 is preferably horizontal. However,the portion of the image displayed is preferably biased toward thedownward portion of the captured image because significantly less usefulinformation is obtained above the horizontal position of the imagecapture devices.

Each image-capturing device 14, 16 is controlled by appropriatesupporting electronics (not shown) located in the vicinity of theimaging array such that, when operating power is supplied, either ananalog or a digital data stream is generated on an output signal linesupplied to image processor 18. The support electronics may be providedpartially on the image chip and partially on associated electronicdevices. For each exposure period, a value indicative of the quantity oflight incident on each pixel of the imaging array during the exposureperiod is sequentially outputted in a predetermined sequence, typicallyrow-by-row. The sequence may conform to video signal standards whichsupport a direct view such that, when a scene is viewed by animage-capturing device, the image presented on a display representsdirectly the scene viewed by the image-capturing devices. However, whenlooking forward and observing a displayed image of a rearward scene, thedriver will interpret the image as if it were a reflection of the sceneas viewed through a mirror. Objects to the left and rearward of thevehicle, as viewed by the rearward-looking camera, are presented on theleft-hand side of the display and vice versa. If this reversal iseffected in image processor 18, it may be by the use of a data storagedevice, or buffer, capable of storing all of the pixel values from oneexposure period. The data is read out of the data storage device in areversed row sequence. Alternatively, the imaging array electronicscould be constructed to provide the above-described reversal at theimage-capturing device or at the display.

Data transmission between image capture devices 14, 16 and imageprocessor 18 and/or between image processor 18 and display 20 may be byelectrically conductive leads. The leads may comprise either a serial orparallel bus. Alternatively, the data transmission may be via plastic orglass fiber-optic cable or an RF link. It is possible, for particularapplications, to eliminate image processor 18 and direct drive display20 from image capture devices 14, 16 at the pixel level. This may beaccomplished by providing an interface between the output of imagecapture device 14, 16 and display 20 which synchronously maps imagepixels captured by the image capture device, or devices, to the display.This synchronous mapping may be accomplished by providing a one-to-onemapping in which each pixel measurement is communicated to the display.Alternatively, the interface may only transmit pixel data whichrepresents changes in the captured image. This allows for a reduction inthe communication bandwidth necessary to transmit data between the imagecapture device, or devices, and the display. This may be accomplished byencoding the pixel data which represents changes in the captured imagewith additional data which designates the position of the pixel or otherrelevant information. Communication between the image capture device, ordevices, may be multiplexed.

The data streams from image-capturing devices 14, 16 are combined inimage processor 18 and directly mapped to the pixel array of display 20.This process is repeated preferably at a rate of at least 30 times persecond in order to present an essentially real time video image. Theimage captured by side image capture device 14 on the right side of thevehicle is presented in right image portion 46 and the image from sideimage capture device 14 on the left side of the vehicle is displayed onleft image portion 44. The image from center image capture device 16 isdisplayed on central image portion 48. The three image portions 44-48are presented in horizontal alignment and adjacent to each other.However, the composite image may be positioned at any desired verticalposition in the display 20. It is also possible to display imageportions 44-48 on separate image devices which are adjacent each other.

In vision system 12, side image capture devices 14 are positionedpreferably at a forward longitudinal position on vehicle 10 and centerimage capture device 16 is positioned at a rearward longitudinalposition on the vehicle. As best seen by reference to FIG. 7, thispositioning creates a difference in the vertical angle between each sideimage capture device 14 and center image capture device 16 with respectto a fixed location P1 that is a distance D1 behind the vehicle. Thisdifference in sensing angle will cause each side image capture device 14to image an object located at P1 on a horizontal row of pixels that isdifferent from the horizontal row of pixels that center image capturedevice 16 will image the same object. If the image is below thehorizontal centerline of the image capture device, it will be imaged ona lower row of pixels by center image capture device 16 than the row ofpixels it will be imaged by the side image capture devices 14, asillustrated in FIG. 7. This mismatch between horizontal pixel rows ofthe captured image is furthermore a function of the distance of thecaptured image from the rear of the vehicle. This can be understood byreference to FIG. 11 which presents a chart 90 having a first column 92of pixel lines n1, measured from the array centerline, at which anobject will be imaged by side image capture device 14 and a secondcolumn 94 of pixel lines n2, measured from the array verticalcenterline, at which the same object will be imaged by center imagecapture device 16. The result is that an object, which is captured byboth side and center image capture devices 14, 16, will be verticallydisjointed at the boundary of the displayed image, if the object iscaptured by more than one image capture device. The amount ofdisjointment will be greater closer to the vehicle and less at furtherdistances. If the object is elongated in the horizontal direction, suchas earth's horizon, bridges, or cross-markings on highways, then theobject will appear to be either broken or crooked.

In order to provide uniform display of laterally elongated images, arearview vision system 12′ is provided having a central image portion48′ which is processed differently from the image display portions 44′and 46′ produced by the side image capture devices (FIG. 8). Centralimage portion 48′ is reduced vertically, or compressed, by removingspecified scan lines, or pixel rows, from the image captured by centerimage capture device 16 in a graduated fashion. The difference in thepixel line at which an object will be imaged by each of the side andcenter image capture devices is a function of the distance D of theobject from the rear of the vehicle, with a greater variation occurringat shorter distances and the variation reducing to zero for infinitedistances. Therefore, the compression of central image portion 48′ isnon-linear, with substantially no compression at the vertical center ofthe image and greater compression at greater distances above and belowthe vertical center point of the image. This is accomplished by removingspecific lines from the center display in a graduated fashion with agreater number of lines removed further from the vertical center of theimage. The removed lines may be merely discarded in order to verticallyreduce the image. Alternatively, the data contained in the removed linesmay be utilized to modify the value of adjacent pixels above and belowthe removed line in order to enhance the quality of the compressedimage. Averaging, median filtering, or other such known techniques mayalso be used.

Each of right image portion 46′ and left image portion 44′ includes anupper portion 64 which extends above the compressed upper portion of thecentral image portion 48′. In the illustrated embodiment, upper portions64 are deleted in order to present a uniform upper horizontal boundaryfor display 20′. In the illustrated embodiment, the mismatch between thelower horizontal boundary of central image portion 48′ and each of theleft and right image portions provides a dead space 66 which provides avisual prompt to the user of the approximate location of the rearwardcorners S of vehicle 10. This dead space 66 in the image displayed ondisplay 20′ approximates the footprint occupied by vehicle 10 whenviewed from point C. This is particularly useful because it provides avisual indication to the driver that a vehicle passing vehicle 10, asviewed in either left image portion 44′ or right image portion 46′, isat least partially adjacent vehicle 10 if the image of the approachingvehicle is partially adjacent to dead space 66.

In an alternative embodiment, the vertical compression technique may beapplied to only a lower vertical portion of central image portion 48′.In most driving situations, objects imaged by rearward-facing imagecapture devices above the horizon are at a long distance from thevehicle while those below the horizon get progressively closer to thevehicle in relation to the distance below the horizon in the displayedimage. Therefore, compression of the upper vertical portion of thecentral image portion may be eliminated without significant reduction inperformance.

Compression of the central image portion may also advantageously beprovided horizontally, as well as vertically. Spatial separation ofcenter image capture device 16 from side image capture devices 14 causessimilar distortion, as that described above, in the horizontaldirection. This effect is spherical in nature and would require a morecomplex corrective action, such as compressing the image based upon theremoval of pixels from an approximation to concentric circles centeredon the center of the imaging array, or other techniques which would beapparent to those skilled in the art.

A rearview vision system 12″ includes an image display 20″ having acompressed central image portion 48″ and left and right image portions44″ and 46″, respectively (FIG. 10). A border 50′ between left sideimage 44″ and central image 48″ includes a vertical central borderportion 50 a′, an upper border portion 50 b′, and a lower border portion50 c′. Upper border portion 50 b′ and lower border portion 50 c′ divergelaterally outwardly, vertically away from central portion 50 a′. Aborder 52′ between central image portion 48″ and right image portion 46″includes a central boundary portion 52 a′, an upper boundary portion 52b′, and a lower boundary portion 52 c′. Upper boundary portion 52 b′ andlower boundary portion 52 c′ diverge laterally outwardly vertically awayfrom central portion 52 a′. This creates an upper portion of centralimage portion 48″ and a lower portion of central image portion 48″ whichextend beyond the center portion thereof. This configuration is basedupon the realization that the surface of the road immediately behind thevehicle is captured by central image capture device 16. Likewise, thehorizontal plane above the vehicle, which is symmetrical with the roadsurface, is captured by the center image capture device. This may beseen by referring to point P in FIG. 10, which illustrate the pointswhere the effective radius 68 of the virtual image capture deviceintersects dead zones 30 and by referring to point S in FIG. 10 whichillustrates the corners or the rear of the vehicle (S).

The image displayed on display 20″ includes a dead space 66′ havingdiverging lateral sides 68 a, 68 b. Diverging sides 68 a and 68 b areconfigured in order to extend in the direction of travel of vehicle 10which is parallel to lane markings of a highway on which vehicle 10 istravelling. This further enhances the visual perception of the driver byproviding a visual clue of the location of images appearing on display20″ with respect to the vehicle 10. Side portions 68 a, 68 b, in theillustrated embodiment, are natural extensions of lower boundaryportions 50 c′ and 52 c′ and extend from point S on each respective sideof the vehicle to point R, which represents the intersection of thelower extent of the vertical field of view 40 of each side image capturedevice 14 with the pavement (FIG. 7).

Rearview vision systems 12′ and 12″ utilize a displayed synthesizedimage which takes into account the use of perspective in enhancing thedriver's understanding of what is occurring in the area surrounding thevehicle. The images produced on displays 20′ and 20″ effectively removethe vehicle bodywork and replace the bodywork with a vehicle footprintas would be viewed by virtual camera C. The image displayed on display20″ further includes perspective lines which further enhance the roll ofperspective in the driver's understanding of what is occurring.

In order to further enhance the driver's understanding of what isoccurring in the area surrounding the vehicle, a rearview vision system12′ includes a display 20′ having image enhancements (FIG. 6). In theillustrative embodiment, such image enhancements include graphicoverlays 70 a, 70 b which are hash marks intended to illustrate to thedriver the anticipated path of movement of vehicle 10. In theillustrated embodiment, the anticipated vehicle motion is a function ofthe vehicle direction of travel as well as the rate of turn of thevehicle. The forward or rearward direction of vehicle travel isdetermined in response to the operator placing the gear selection device(not shown) in the reverse gear position. The degree of turn of thevehicle may be determined by monitoring the movement of the vehiclesteering system, monitoring the output of an electronic compass, ormonitoring the vehicle differential drive system. In the embodimentillustrated in FIG. 6, the configuration of graphic overlays 70 a, 70 bindicates that the vehicle is in reverse gear and that the wheels areturned in a manner that will cause the vehicle to travel toward thedriver's side of the vehicle. If the wheels were turned in the oppositedirection, graphic overlays 70 a, 70 b would curve clockwise toward theright as viewed in FIG. 6. If the vehicle's wheels were straight,graphic overlays 70 a, 70 b would be substantially straight converginglines. If the vehicle is not in reverse gear position, graphic overlays70 a, 70 b are not presented. Other types of graphic overlays of thedisplayed image are comprehended by the invention.

Horizontal grid markings on the display may be provided to indicatedistances behind the vehicle at particular markings. Such grid wouldallow the driver to judge the relative position of vehicles behind theequipped vehicle. In one embodiment, short horizontal lines aresuperimposed on the displayed image at regular rearward intervals inhorizontal positions which correspond to the boundaries of the lane inwhich the vehicle is travelling. In order to avoid confusion when thevehicle is travelling in a curved path, from a lack of correspondencebetween the graphic overlay and the road, a signal indicative of thevehicle's rate of turn may be taken into account when generating thegraphic overlay. In this manner, the distance indications may be movedlaterally, with reduced horizontal separation, to correspond to thepositions of the curved lane boundaries and vertically on the image tocompensate for the difference between distances along a straight andcurved path.

Another image enhancement is to alter the appearance of an object in aparticular zone surrounding the vehicle in order to provide anindication, such as a warning, to the driver. As an example, a vehiclethat is too close to the equipped vehicle for safe-lane change, may bedisplayed in a particular color, such as red, may flash, or otherwise bedistinguishable from other images on the display. Preferably, the speedof the equipped vehicle 10, which may be obtained from known speedtransducers, may be provided as an input to the rearview vision systemin order to cause such warning to be a function of the vehicle speedwhich, in turn, affects the safe separation distance of vehicles. Theoperation of the turn signal may also be used to activate suchhighlighting of other road users or to modify the scope of the imagedisplayed. In order to determine the distance of objects behind vehicle10, a separate distance-measuring system may be used. Such separatesystem may include radar, ultrasonic sensing, infrared detection, andother known distance-measuring systems. Alternatively, stereoscopicdistance-sensing capabilities of side image capture devices 14 may beutilized to determine the separation distance from trailing objectsutilizing known techniques.

Thus, it is seen that the image displayed on display 20-20′″ may bedifferent under different circumstances. Such different circumstancesmay relate to the vehicle's direction of travel, speed, rate of turn,separation from adjacent objects, and the like.

Various other forms of image processing may be utilized with rearviewvision system 12-12′″. Luminant and chrominant blending may be appliedto the images captured by image capture devices 14, 16 in order toproduce equality of the image data whereby the image portions appear asif they were produced by one image capture device. The dynamic range ofthe image capture devices may be extended in order to provide highquality images under all lighting conditions. Furthermore, individualpixel groups may be controlled in order to selectively compensate forbright or dark spots. For example, anti-blooming techniques may beapplied for bright spots. Multiple exposure techniques may be applied tohighlight dark areas. Image morphing and warping compensation techniquesmay additionally be applied. Resolution of the image capture devices anddisplay may be selected in order to provide sufficient image quality forthe particular application.

A heater may be applied to each image capture device in order to removedew and frost that may collect on the optics of the device. Although, inthe illustrative embodiment, the optical centerline of the cameracoincides with the field of view, particular applications may result inthe centerline of the camera pointing in a direction other than thecenterline of the field of view. Although, in the illustrativeembodiment, the image capture devices are fixed, it may be desirable toprovide selective adjustability to the image capture devices or opticalpaths in particular applications. This is particularly desirable whenthe system is used on articulated vehicles where automated andcoordinated camera aim may be utilized to maintain completeness of thesynthesized image.

When operating the vehicle in the reverse direction, it may be desirableto provide additional data concerning the area surrounding the immediaterear of the vehicle. This may be accomplished by utilizingnon-symmetrical optics for the center image capture device in order toprovide a wide angle view at a lower portion of the field of view.Alternatively, a wide angle optical system could be utilized with theelectronic system selectively correcting distortion of the capturedimage. Such system would provide a distortion-free image while obtainingmore data, particularly in the area surrounding the back of the vehicle.

The invention additionally comprehends the use of more than three imagecapture devices. In addition to side image capture devices positioned atthe front sides of the vehicle and a center image capture devicepositioned at the center rear of the vehicle, additional image capturedevices may be useful at the rear corners of the vehicle in order tofurther eliminate blind spots. It may additionally be desirable toprovide an additional center image capture device at a higher elevationin order to obtain data immediately behind the vehicle and thereby fillin the road surface detail immediately behind the vehicle. Suchadditional detail is particularly useful when operating the vehicle inthe reverse direction. Of course, each of the image capture devicescould be a combination of two or more image capture devices.

Although the present invention is illustrated as used in a rearviewvision system, it may find utility in other applications. For example,the invention may be useful for providing security surveillance in anarea where a building or other object obstructs the view of the areaunder surveillance. Additionally, the invention may find application innight-vision systems and the like. For example, the invention may beapplied to forward-facing night-vision systems, or other visionenhancement systems such as may be used in adverse weather oratmospheric conditions such as fog, applied to provide an enhanceddisplay of a synthesized image, which approximates a forward-facing viewfrom a single virtual camera located rearwardly of the driver, takingadvantage of the perspective features of the image.

A rearview vision system 150 is provided which, in addition todisplaying a rear image on display 20 which is synthesized by imageprocessor 18 from the output of image capture devices 14, 16, alsosupplies drive signals to an electrically operated optical device suchas electro-optic mirror 152, an electro-optic window 154, or both. Eventhough a panoramic view rearward of the vehicle is displayed on display20, it may be desired to provide the driver with a rearview mirror ofthe type which has conventionally been provided on vehicles. One suchmirror is an electro-optic mirror, such as an electrochromic mirror, aliquid crystal mirror, or a solenoid-operated prismatic mirror and thelike. Additionally, vehicles may be provided with electro-optic windows,such as sunroofs, rear windows, side windows, and the like, which changetransmissivity in response to a drive signal to a partial lighttransmittance level. In U.S. patent application Ser. No. 08/023,918filed Feb. 26, 1993, by Kenneth Schofield and Mark Larson for anAUTOMATIC REARVIEW MIRROR SYSTEM USING A PHOTOSENSOR ARRAY, now U.S.Pat. No. 5,550,677, the disclosure of which is hereby incorporatedherein by reference, a technique is disclosed for producing a drivesignal for an electrically operated optical device, such as anelectro-optic mirror or window, from the image captured by arearward-facing array. Utilizing the techniques disclosed therein, imageprocessor 18 produces a drive signal on line 156 in order to control thepartial reflectance level of electro-optic mirror 152 and a drive signalon line 158 in order to control the partial light transmittance level ofelectro-optic window 154.

A rearview vision system 160 is provided which includes a near infraredillumination device 162 in order to enhance an image captured by imagecapture devices 14, 16 (FIG. 19). In the illustrated embodiment,infrared illumination device 162 illuminates an area immediately behindthe vehicle. Preferably, the output of illumination device 162 has agreater near infrared light output than visible light output. Thisallows an enhanced image to be captured by the image capture devicewithout increasing the visible light perceived by drivers surroundingthe vehicle. Infrared illumination device 162 may be actuated inresponse to the vehicle being placed in reverse gear. This providesbackup illumination which is greatly enhanced without having anincreased effect on other drivers. Alternatively, infrared illuminationdevices may be positioned, for example, at other locations on the sideor even the front of a vehicle in order to enhance the image captured bythe image capture device or devices. This is especially useful in orderto utilize rearview vision system 160 with a large truck, such as atrailer truck. This infrared illumination device may flood the areaaround the trailer with infrared light in order to enhance the imagecaptured by the image capture device, or devices, without distractingother drivers.

Image capture device 14, 16 may include a housing 164 in which anantenna 166 is positioned. This provides a convenient and functionallocation for a receiving antenna, such as the type used with a globalpositioning system, cellular telephone, garage door opener, radardistance sensing device, and the like, as disclosed in patentapplication Ser. No. 08/569,851 filed by Desmond J. O'Farrell, Roger L.Veldman and Kenneth Schofield for a VEHICLE GLOBAL POSITIONING SYSTEM,now U.S. Pat. No. 5,971,552, the disclosure of which is herebyincorporated herein by reference. A heater 168 may be associated withthe image capture device in order to stabilize the temperature of thedevice in low ambient temperature conditions. A similar heater may besupplied in display 20 in order to improve its performance in lowambient temperature conditions. A heater control 170 is provided inorder to control the energization of heater 168 and, if utilized, theheater in the display. Heater control 170, preferably, energizes heater168 prior to the vehicle being started. This allows the temperature ofthe image capture device to be elevated to a more desirable temperatureprior to the driver operating the vehicle. This may be accomplished byheater control 170 being a proximity detector which detects a devicecarried by the driver as the driver approaches the vehicle.Alternatively, heater control 170 may be responsive to a signal producedby a remote keyless entry device concurrently with the doors beingactivated. Alternatively, heater control 170 may be responsive to thevehicle device being opened.

A rearview vision system 172 is provided which provides an output,generally referred to at 174, from image processor 18 to display 20.Output 174 provides an indication when an object bears a predeterminedrelationship to the vehicle. Such object may be of interest because theobject is in a blind spot of the vehicle, may be tailgating the vehicle,or may be an object in front of the vehicle which the vehicle is tooclose to. Display 20 may respond to output 174 by highlighting thedisplayed vehicle, such as by displaying the vehicle in an artificialcolor, such as red, by flashing the image of the vehicle, or, otherwise,drawing the attention of the driver to the vehicle. Output 174 may bedeveloped by image processor 18 from the outputs of image capturedevices 14, 16. This may be accomplished by, for example, utilizingredundant image portions captured by the image capture devices, eventhough not displayed by display 20, in order to calculate relativeposition of the object with respect to the vehicle. Alternatively, anobject sensor 176 may be provided in order to supply an output 178indicative of a predetermined positional relationship of an objectsensed by the object sensor with respect to the vehicle. In theillustrated embodiment, object sensor 176 may be a passive infraredsensor which senses the presence of an object in the vehicle's blindspot. Alternatively, object sensor 176 may be a distance-measuringdevice, such as an active infrared sensor, an ultrasonic sensor, a radarsensor, or the like. Such object sensor is especially useful indetermining the separation distance between the vehicle and objects infront of the vehicle. Preferably, object sensor 176 has a sensing fieldof view that is substantially coincident with the field of view of oneor more of the image capture devices 14, 16.

A rearview vision system 178 is provided which has the capability ofdisplaying stereoscopic images rearward of the vehicle. Rearview visionsystem 178 includes at least one pair of image capture devices 14 a,which are closely positioned on the vehicle and have overlapping fieldsof view. Because the image capture device pairs are closely positioned,they capture substantially the same image but from a slightly differentangle. This allows image processor 18 to produce a video signal 100′with stereoscopic information. This signal is utilized by a stereoscopicdisplay 320 in order to produce a stereoscopic image rearward of thevehicle. Such stereoscopic displays are known in the art. Although onepair of image capture devices are illustrated in FIG. 22, rearviewvision system 178 may include multiple pairs of image capture devices.This allows a rear image to be synthesized from the multiple pairs ofimage capture devices in order produce a panoramic view rearward of thevehicle and stereoscopic image. Preferably, utilizing other aspects ofthe invention, the stereoscopic image is a rearward-facing view from asingle location.

A rearview vision system 180 is provided which produces an indication182 of road line markings. Indication 182 may also indicate road edges.Image processor 18 detects the road line markings and the road edgesfrom the images captured by image capture devices 14, 16. This featuremay be further enhanced by combining it with an infrared illuminationdevice 162 in order to further illuminate areas behind and around thevehicle in order to enhance the image of the road line markings and theroad edges. Indication 182 may be utilized by display 20 in order toprovide an indication of the vehicle with respect to the road linemarkings and road edges. The indication may further be utilized by anindicator which indicates the relative position of the vehicle in itslane. Additionally, the indication may be utilized to determine eroticvehicle operation, such as may occur when the driver begins to fallasleep, in order to provide a suitable alarm, or the like.

A rearview vision system 184 is provided with capabilities for infraredcommunication with other vehicles and stationary beacons. Rearviewvision system 184 produces a communication data output 186 whichincludes communication data decoded from infrared signals detected byimage capture device or devices 14, 16. For example, suitable standardsmay be developed wherein vehicles are equipped with a pair of spacedapart infrared transmitters on a forward portion thereof. Imageprocessor 18 may respond to the temporal and spatial patterns ofinfrared signals detected by image capture devices 14, 16 in order todetermine the speed and distance and, thereby, the separation of thevehicles as well as the rate of change of separation of the vehicles.Such information may be communicated to the trailing vehicle by aninfrared transmitter (not shown) in order to control the speed of thetrailing vehicle. This feature provides adaptive cruise control in whichthe speed of the trailing vehicle is controlled according to separationdistance with leading vehicles. This allows high-speed convoying betweenvehicles. The communication system may additionally provide for theidentification of emergency vehicles, and the like, which may transmit aunique temporal and/or spatial pattern of an infrared signal. The IRcommunication signal may additionally be utilized to receive signalsfrom stationary devices, such as location beacons and IntelligentVehicle Highway System (NHS) data. Because rearview vision system 184has a field of view which extends generally rearwardly of the vehicle,the system provides the capability for sensing information after thevehicle has passed the beacon. This provides an adjunct to infraredcommunication systems having a field of view generally forward of, or tothe side of, the vehicle.

A rearview vision system 188 is provided having extended dynamic range(FIG. 25). Rearview vision system 188 includes a pair of image capturedevices 14 and/or 16, each of which has an image-sensing array 190. Eachimage capture device is capable of operating in either a color mode, inwhich a color image is displayed on display 20, or a monochrome mode, inwhich a monochrome image is displayed on display 20. System 188 includesan image luminance sensor 192 which senses the luminance level of imagescaptured by image capture devices 14, 16. Image luminance sensor 192 mayswitch the image capture devices between the color mode and themonochrome mode such that, when the image luminance is sufficientlyhigh, the image capture device, or devices, operate in a color mode.During low image luminance conditions, the image capture device, ordevices, are operated in a monochromatic mode which does not require asmuch image luminance. This extends the dynamic range of the system.Rearview vision system 188 may additionally include an exposure control194 which determines the exposure period for capturing each frame byarrays 190. In order to extend the dynamic range of system 188, exposurecontrol 194 may produce exposure intervals for arrays 190 which vary inlength from interval-to-interval. Thus, a series of normal exposureintervals may be occasionally supplanted by a longer exposure intervalduring which greater detail of the image may be captured. This enhancedimage may then be combined with the image captured during the shorterintervals into a merged image of enhanced detail.

Rearview vision system 188 may additionally include a plurality ofinfrared shutters 196 which are in the optical paths 198 of arrays 190.Each infrared shutter 196 has at least one state in which infraredenergy is generally not attenuated to array 190. In another state, theinfrared shutter generally blocks infrared radiation from the array. Thestate of infrared shutters 196 is controlled by image luminance sensor192. During periods of high image luminance, sensor 192 may switch theinfrared shutters 196 to a state blocking near infrared radiation fromarrays 190. However, during low image luminance conditions, sensor 198may switch the infrared shutters 196 to a state in which the nearinfrared energy is transmitted to arrays 190. The addition of the nearinfrared radiation at low luminance levels enhances the image luminancesensed by arrays 190. In the illustrated embodiment, infrared shutters196 are either electrochromic shutters or liquid crystal shutters, bothof which are known in the art. Rearview vision system 188 additionallyincludes means for coordinating the image intensity received frommultiple image capture devices and displayed on display 20. This allowsa balance composite image to be displayed on the display. This may beprovided by a display intensity control 200 which regulates theintensity of the output of both arrays 190 in order to produce color andluminance balancing between the multiple image capture devices. Insteadof a separate display intensity control, a direct communication channelmay be developed between the image capture devices in order to providecolor and luminance balancing.

Each image pixel captured by image capture devices 14, 16 and displayedon display 20 has a resolution which affects the amount of image detaildisplayed. While it is desirable to have a high degree of detail ofdisplayed image, the increase in image resolution produces acommensurate increase in system cost. While it is desirable to reducesystem cost, this should not be achieved by sacrificing necessary detailin the displayed image. According to the invention, it has beendetermined that sufficient image detail may be obtained at a suitablesystem cost by having a pixel resolution in the range of betweenapproximately 2 arc minutes and approximately 8 arc minutes. Preferably,system resolution is approximately 6 arc minutes.

It is known in the art to provide imaging array capture devices havingmosaic filters which mask image radiation in order to produce pixelswhich respond respectively to red, green, and blue light. Because suchknown pixel filter masks do not adequately absorb near infraredradiation, it is known to supply infrared filters in order to blockinfrared radiation from the pixels so that the pixels respond to onlythe designed radiation band. However, such additional filters haveundesirable characteristics including costs. It has been discovered thata pixel filter mask may be made responsive to red, green, or blue lightwhile filtering out near infrared by adding appropriate dyes to the dyesmaking up the filter mask.

The heater supplied with each image capture device may include atransparent conductive coating applied to a window covering the devicelens. Alternative heater constructions include ITO or a series of finewire mesh. This provides protection of the lens of the image capturedevice from physical harm while allowing moisture and frost to beremoved from the window.

Various manipulation techniques may be applied to image capture devices14, 16. For example, when the invention is applied tosemi-tractor/trailer combinations, the image capture devices may bemotorized and responsive to signals representing the relative positionof the trailer and the cab in order to produce full panoramic viewduring various maneuvers of the vehicle. For example, as the vehicleturns, which may cause the trailer to otherwise block the image capturedby a side image capture device, the image capture device may pivot to adifferent panoramic view which is not blocked by the trailer.Additionally, the panoramic view sensed by the image capture device maybe different when the trailer is attached than when the trailer is notattached. In a similar fashion, rearward-mounted image capture device 16may be motorized to move vertically upwardly and downwardly between afirst position when the vehicle is moving in a forward direction and asecond position when the vehicle is in reverse gear. In the secondposition, the motorized camera is directed more downwardly in order tocapture images closer to the rear of the vehicle which may be contactedby the vehicle. Image capture devices 14, 16 may be supplied withelectrical opto-mechanical zoom devices as well as vibration isolationand compensation stabilizing devices.

Image processor 18 may provide an input to a control for the intensityof the brake lights, turn signals, and the like for the vehicle. In thismanner, the image processor may control the intensity of such lightsbased upon ambient lighting conditions. This allows the intensity of therearward directed lights to be less distracting for following vehicles.

Additionally, the present invention may be utilized for providingguidance for a tractor/trailer or like vehicle backing to a loadingdock. Additionally, the invention may provide guidance for properalignment of the trailer and tractor which are being joined by backingof the tractor. The present invention may additionally provide accidentmonitoring by capturing a predetermined continuous stream of images,such as, for example, 15 seconds. This running store of image may befrozen upon impact of the vehicle, in order to record events leading upto the impact, or may be stopped by a manual input. Furthermore, theinvention may be utilized to alert the driver to an impending rear-endcollision. The vehicle may respond to such indication by deploying anappropriate device, such as a smart headrest or the like.

Thus, it is seen that the present invention enhances the relationshipbetween the driver's primary view and the image presented on therearview vision system. This is accomplished in a manner which providesease of interpretation while avoiding confusion so that the driver doesnot have to concentrate or look closely at the image. In this manner,information presented on the display is naturally assimilated. This isaccomplished while reducing blind spots so that other vehicles orobjects of interest to the driver will likely be displayed to thedriver. Additionally, the use of perspective allows distances to be moreaccurately determined.

Changes and modifications in the specifically described embodiments canbe carried out without departing from the principles of the invention,which is intended to be limited only by the scope of the appendedclaims, as interpreted according to the principles of patent lawincluding the doctrine of equivalents.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. A vehicle automaticvehicle exterior light control, said vehicle automatic vehicle exteriorlight control comprising: an image sensor disposed at a vehicle andhaving a two-dimensional array of columns and rows of photosensingpixels, wherein said image sensor has a field of view exterior thevehicle and wherein said array of said image sensor comprises morecolumns of photosensing pixels thain rows of photosensing pixels; animage processor operable to process image data captured by said imagesensor; a controller operable, responsive to image processing of aportion of captured image data representative of a portion of the fieldof view of said image sensor and responsive to at least one vehicleinput, to generate at least one vehicle automatic exterior light controlsignal and an exterior light status indicator signal as a function ofsaid image processing of the portion of captured image data and of saidat least one vehicle input; and wherein said controller, responsive toimage processing of captured image data, is operable to detect roadmarkings on a road along which the vehicle is traveling.
 2. The vehicleautomatic vehicle exterior light control of claim 1 wherein said atleast one vehicle input is a speed input.
 3. The vehicle automaticvehicle exterior light control of claim 2 wherein said at least onevehicle input is a compass sensor.
 4. The vehicle automatic vehicleexterior light control of claim 2 wherein said at least one vehicleinput is an auto on/off switch.
 5. The vehicle automatic vehicleexterior light control of claim 1 wherein said at least one vehicleinput is a light sensor.
 6. The vehicle automatic vehicle exterior lightcontrol of claim 1 wherein said controller further comprises at leastone output.
 7. The vehicle automatic vehicle exterior light control ofclaim 1 wherein said controller comprises at least in part said imageprocessor.
 8. The vehicle automatic vehicle exterior light control ofclaim 1 wherein said controller controls a display in response to anambient light input supplied with a signal generated by said imagesensor.
 9. The vehicle automatic vehicle exterior light control of claim1 wherein said vehicle automatic vehicle exterior light control detectsambient light exterior to the vehicle and generates said exterior lightstatus indicator signal to indicate the status of the detected ambientlight.
 10. The vehicle automatic vehicle exterior light control of claim1 wherein said vehicle automatic vehicle exterior light controlcomprises at least one of (a) a headlight control system responsive toambient light detected by sensors and (b) a rearview image displaycontrol system responsive to ambient light at the vehicle.
 11. Thevehicle automatic vehicle exterior light control of claim 1 wherein saidexterior light status indicator signal is via said image sensor.
 12. Thevehicle automatic vehicle exterior light control of claim 1 wherein saidcontroller receives a first image input from a first image sensor and asecond image input from a second image sensor, and wherein saidcontroller generates a composite image synthesized from at least saidfirst image input and said second image input, and wherein a displaysystem displays said composite image on a single video screen located ina cabin of the equipped vehicle and viewable by a driver of the equippedvehicle when the driver is normally operating the equipped vehicle. 13.The vehicle automatic vehicle exterior light control of claim 12 whereina first field of view of said first image sensor and a second field ofview of said second image sensor are directed generally rearwardly withrespect to the direction of travel of the equipped vehicle, and whereinsaid first field of view has a field of view portion at least partiallyoverlapping a field of view portion of said second field of view. 14.The vehicle automatic vehicle exterior light control of claim 13 whereingeneration of said composite image from at least said first and secondimage inputs for display on said single video screen comprises dynamicadaptation of said first and second image inputs in order to minimizesaid at least partially overlapping field of view portion.
 15. Thevehicle automatic vehicle exterior light control of claim 12 whereinsaid single video screen has a display luminance that is variableresponsive to a sensing of an ambient light level.
 16. The vehicleautomatic vehicle exterior light control of claim 15 wherein the displayluminance of said single video screen of said display system is variableresponsive to at least one of (i) a vehicle headlight activationcontrol, (ii) an ambient light sensor, and (iii) an indication ofambient light level developed by at least one of said first and secondimage sensors.
 17. The vehicle automatic vehicle exterior light controlof claim 12 wherein said single video screen is operable to display atleast one of pager information, a telephone number listing, a globalpositioning system output, a map, route guidance information,intelligent vehicle highway system information, vehicle radio controlsettings, vehicle environmental system settings, vehicle speed, vehicleheading, and turn signal indicators.
 18. A vehicle automatic vehicleexterior light control, said vehicle automatic vehicle exterior lightcontrol comprising: an image sensor disposed at a vehicle and having atwo-dimensional array of columns and rows of photosensing pixels,wherein said image sensor has a field of view exterior the vehicle andwherein said array of said image sensor comprises more columns ofphotosensing pixels than rows of photosensing pixels; an image processoroperable to process image data captured by said image sensor; acontroller comprising at least one output, wherein said controller isoperable, responsive to image processing of a portion of captured imagedata representative of a portion of the field of view of said imagesensor, to control said at least one output and to generate an exteriorlight status indicator signal as a function of said image processing ofthe portion of captured image data; and wherein said controller,responsive to image processing of captured image data, is operable todetect road markings on a road along which the vehicle is traveling. 19.The vehicle automatic vehicle exterior light control of claim 18 whereinsaid controller further comprises at least one vehicle input.
 20. Thevehicle automatic vehicle exterior light control of claim 19 whereinsaid at least one input is a speed input.
 21. The vehicle automaticvehicle exterior light control of claim 19 wherein said at least oneinput is a manual user input switch.
 22. The vehicle automatic vehicleexterior light control of claim 18 wherein said at least one output isconfigured to control at least one exterior light.
 23. The vehicleautomatic vehicle exterior light control of claim 22 wherein said atleast one output is configured to control at least one electrochromicelement.
 24. The vehicle automatic vehicle exterior light control ofclaim 18 wherein said at least one output is configured to control atleast one headlamp.
 25. The vehicle automatic vehicle exterior lightcontrol of claim 18 wherein said controller comprises at least in partsaid image processor.
 26. The vehicle automatic vehicle exterior lightcontrol of claim 18 wherein said controller controls a display inresponse to an ambient light input supplied with a signal generated bysaid image sensor.
 27. The vehicle automatic vehicle exterior lightcontrol of claim 26 wherein said signal is based on an average intensityvalue sensed by at least some of said pixels of said image sensor. 28.The vehicle automatic vehicle exterior light control of claim 18 whereinsaid vehicle automatic vehicle exterior light control detects ambientlight exterior to the vehicle and generates said exterior light statusindicator signal to indicate the status of the detected ambient light.29. The vehicle automatic vehicle exterior light control of claim 18wherein said vehicle automatic vehicle exterior light control comprisesat least one of (a) a headlight control system responsive to ambientlight detected by sensors and (b) a rearview image display controlsystem responsive to ambient light at the vehicle.
 30. The vehicleautomatic vehicle exterior light control of claim 18 wherein saidvehicle automatic vehicle exterior light control comprises (a) aheadlight control system responsive to ambient light detected by sensorsand (b) a rearview image display control system responsive to ambientlight at the vehicle.
 31. The vehicle automatic vehicle exterior lightcontrol of claim 18 wherein said exterior light status indicator signalis via said image sensor.
 32. The vehicle automatic vehicle exteriorlight control of claim 18 wherein said vehicle automatic vehicleexterior light control is operable to (a) generate an automatic exteriorlight control signal responsive to light sensors and (b) generate saidexterior light status indicator signal via said image sensor.
 33. Avehicle automatic vehicle exterior light control, said vehicle automaticvehicle exterior light control comprising: an image sensor disposed at avehicle and having a two-dimensional array of columns and rows ofphotosensing pixels, wherein said image sensor had a field of viewexterior the vehicle and wherein said array of said image sensorcomprises more columns of photosensing pixels than rows of photosensingpixels; an image processor operable to process image data captured bysaid image sensor; a controller comprising at least one output, whereinsaid output and an exterior light status indicator signal are functionsof image processing of at least a portion of captured image data andwherein said controller is further configured to receive at least onevehicle input; and wherein said controller, responsive to imageprocessing of captured image data, is operable to detect road markingson a road along which the vehicle is traveling.
 34. The vehicleautomatic vehicle exterior light control of claim 33 wherein said atleast one input is a speed input.
 35. The vehicle automatic vehicleexterior light control of claim 33 wherein said at least one input is acompass sensor.
 36. The vehicle automatic vehicle exterior light controlof claim 33 wherein said at least one output is configured to control atleast one electrochromic element.
 37. The vehicle automatic vehicleexterior light control of claim 33 wherein said at least one output isconfigured to control at least one exterior light.
 38. The vehicleautomatic vehicle exterior light control of claim 33 wherein saidcontroller comprises at least in part said image processor.
 39. Thevehicle automatic vehicle exterior light control of claim 33 whereinsaid controller controls a display in response to an ambient light inputsupplied with a signal generated by said image sensor.
 40. The vehicleautomatic vehicle exterior light control of claim 33 wherein saidvehicle automatic vehicle exterior light control detects ambient lightexterior to the vehicle and generates said exterior light statusindicator signal to indicate the status of the detected ambient light.41. The vehicle automatic vehicle exterior light control of claim 33wherein said vehicle automatic vehicle exterior light control comprisesat least one of (a) a headlight control system responsive to ambientlight detected by sensors and (b) a rearview image display controlsystem responsive to ambient light at the vehicle.
 42. The vehicleautomatic vehicle exterior light control of claim 33 wherein saidexterior light status indicator signal is via said image sensor.
 43. Thevehicle automatic vehicle exterior light control of claim 33 whereinsaid vehicle automatic vehicle exterior light control is operable to (a)generate an automatic exterior light control signal responsive to lightsensors and (b) generate said exterior light status indicator signal viasaid image sensor.
 44. The vehicle automatic vehicle exterior lightcontrol of claim 33 wherein said vehicle automatic vehicle exteriorlight control detects ambient light exterior to the vehicle andgenerates said exterior light status indicator signal to indicate thestatus of the detected ambient light.
 45. A vehicle automatic vehicleexterior light control, said vehicle automatic vehicle exterior lightcontrol comprising: an image sensor disposed at a vehicle and having atwo-dimensional array of columns and rows of photosensing pixels,wherein said image sensor has a field of view exterior the vehicle andwherein said array of said image sensor comprises more columns ofphotosensing pixels than rows of photosensing pixels; an image processoroperable to process image data captured by said image sensor; acontroller operable, responsive to image processing of a portion ofcaptured image data representative of a portion of the field of view ofsaid image sensor and responsive to at least one vehicle input, togenerate at least one vehicle automatic exterior light control signaland an exterior light staus indicator signal as function of said imageprocessing of the portion of captured image data and of said at leastone vehicle input; wherein said controller comprises at least in partsaid image processor; wherein said at least one vehicle input comprisesat least one of (a) a speed input and (b) an auto on/off switch; whereinsaid controller further comprises at least one output: wherein saidcontroller, responsive to image processing of captured image data, isoperable to detect road markings on a road along which the vehicle istraveling.
 46. A vehicle automatic vehicle exterior light control, saidvehicle automatic vehicle exterior light control comprising: an imagesensor disposed at a vehicle and having a two-dimensional array ofcolumns and rows of photosensing pixels, wherein said image sensor has afield of view exterior the vehicle and wherein said array of said imagesensor comprises more columns of photosensing pixels than rows ofphotosensing pixels; an image processor operable to process image datacaptured by said image sensor; a controller comprising at least oneoutput, wherein said controller is operable, responsive to imageprocessing of portion of captured image data representative of a potionof the field view of said image sensor, to control said at least oneoutput and to generate an exterior light status indicator signal as afunction of said image processing of the portion of captured image data;wherein said controller comprises at least in part said image processor;wherein said controller further comprises at least one vehicle input,and wherein said at least one vehicle input comprises at least one of(a) a speed input and (b)a manual user input switch; wherein said atleast one output is configured to control at least one headlamp, andwherein said controller, responsive to image processing of capturedimage data, is operable to detect road markings on a road along whichthe vehicle is traveling.
 47. A vehicle automatic vehicle exterior lightcontrol, said vehicle automatic vehicle exterior light controlcomprising: an image sensor disposed at a vehicle and having atwo-dimensional array of columns and rows of photosensing pixels,wherein said image sensor has a field of view exterior the vehicle andwherein said array of said image sensor comprises more columns ofphotosensing pixels than rows of photosensing pixels; an image processoroperable to process image data captured by said image sensor; acontroller comprising at least one output, wherein said controller isresponsive to image processing of at least a portion of captured imagedata representative of a portion of the field of view of said imagesensor, and wherein said output and an exterior light status indicatorsignal are functions of said image processing of the portion of capturedimage data, wherein said controller is further configured to receive atleast one vehicle input; wherein said controller comprises at least inpart said image processor; wherein said at least one input is a speedinput; wherein said at least one output is configured to control atleast one exterior light; and wherein said controller, responsive toimage processing of captured image data, is operable to detect roadmarkings on a road along which the vehicle is traveling.